1. Field of the Invention
This invention relates to a system and an apparatus for, and a method of compressing an expandable medical device, for example, a stent, and for loading the compressed device into a sheath.
2. Description of Related Art
Intraluminally delivered expandable medical devices have been used to treat damaged or diseased body lumens. Many structures and functions are known in the art. For example, expandable medical devices, namely stent grafts, have been used to treat aortic and thoracic abdominal aneurysms. Expandable medical devices include, but are not limited to, stents, stent grafts, and vena cava filters.
Expandable medical devices may be delivered and deployed using various techniques. For example, a compressed, self-expanding stent graft may be intraluminally delivered and deployed using a catheter delivery system. A stent graft is placed in a radially reduced configuration within the lumen of a catheter or sheath. The catheter is inserted into the vasculature, whereupon the stent graft is delivered to the deployment site. Once the stent graft is properly positioned, the sheath is withdrawn from the stent graft so that the stent graft is allowed to radially expand within the body lumen.
Various apparatuses have been provided for compressing an expandable medical device and for loading the compressed device into a sheath. Examples of such apparatuses are described in U.S. Pat. No. 6,629,350, entitled “Stent Crimping Apparatus and Method,” which is herein incorporated by reference. Typically, a compressor is provided that includes a plurality of blades that forces the device into a compressed configuration. Once the device is compressed, a pusher is used to force the device out of the compressor and into the sheath.
Such a pusher must provide sufficient force to overcome the frictional resistance that can build up between the medical device and the blades. This resistance can be particularly large where the medical device is self-expanding and is biased against the blade surfaces. Prior art apparatuses are effective for compressing and loading short devices and for compressing and loading relatively rigid devices that possess a column strength that is sufficient to withstand the force exerted by the pusher. Longer and/or axially flexible medical devices may present challenges where they do not possess sufficient column strength, and can buckle or crush under the force of the pusher.